Women now account for the majority of people hospitalized with COVID-19 in Quebec, with a clear gap observed in some of the younger age groups. A trend reversal that experts are struggling to explain.
Since the beginning of the pandemic (except during the first wave, which mowed down thousands of seniors in CHSLDs), men with COVID-19 had always been more likely than women to be hospitalized, and this, in all age groups, with rare exceptions.
But the trend was reversed during the Omicron wave last December. The phenomenon, which could have been temporary or the result of chance, continued during the sixth wave and has persisted since the beginning of the seventh. Women now form the majority of people hospitalized with a primary or secondary diagnosis related to COVID-19.
From 45.6% in the fourth wave, the share of women admitted to hospital of the total admissions related to COVID-19 increased to 50.1% in the fifth wave, then to 50.9% in the sixth, and remains at 50.3% so far in the seventh.
At the start of the pandemic, experts attributed the fact that more men infected with SARS-CoV-2 were hospitalized or died from a severe form of COVID-19 to differences in the immune system response of men and women.
A real difference?
However, this recent reversal of the trend has been observed in particular among women aged 20 to 39, who have been hospitalized more often with COVID-19 than men of the same age since the fifth, sixth and seventh waves.
Data published by the INSPQ show that approximately three times as many young women as young men in this age group were hospitalized while infected (129 women versus 40 men hospitalized per 100,000 people in 20-29 years old in the fifth wave; 150 women against 52 men out of 100,000 among 30-39 year olds).
This trend continued during the sixth and seventh waves, but the experts consulted are struggling to explain these differences. “When we look at this, we wonder: is it linked to an epidemiological, sociological or biological factor? » raises the Dr Don Vinh, infectious disease specialist at the McGill University Health Center and expert in immunology.
Women generally fight COVID-19 better than men, confirms the Dr Vinh. But they may be more likely to have been infected recently because of their profession or their increased exposure to children, he suggests.
Biologically, no scientific data indicates that women are more vulnerable to the Omicron variant or to the BA.4 and BA.5 sub-variants, he points out.
The statistics are far from sharp, it harms prevention policies
The lack of data on the actual incidence of infections since January does not allow clear conclusions to be drawn, deplores the infectious disease specialist. “For months, we have been sailing a little blind. It is not known who is the most infected. There could be bias in the results. It could also be that a perfect storm creates this gap in young people. But the statistics are far from accurate, it harms prevention policies. »
According to epidemiologist Benoît Mâsse, from the University of Montreal, the data published by Quebec are too incomplete to draw conclusions on the apparent gap in hospitalizations among young adults. They could even create a “distortion” hiding a greater difference or contrary trend, he warns.
One thing is certain, since the sixth wave, the “official” number of COVID-19 cases reported by Quebec is twice as high among women as among men, due to screening limited to priority clienteles, often female: health personnel, school personnel and residents of CHSLDs and RPAs.
The probes conducted every two weeks by the INSPQ to try to assess the real number of cases in Quebec also indicate that the majority of people infected since last May are women.
A hypothesis
According to the DD Caroline Quach, pediatrician and infectiologist at the Sainte-Justine University Hospital Center (CHU), the lack of data on the actual infection rate by sex, the root cause of hospitalizations and the profile of patients (patients at risk, prior medical problems , etc.) makes any conclusion difficult.
She hypothesizes that young women may present, unlike men, with pregnancy as an increased risk factor for admission due to COVID. “There is more risk of hospitalization (during pregnancy) and also a tendency to be more careful with a pregnant mom,” she replied by email.
A cross-Canada study found that between March 2020 and October 2021, 7.7% of infected pregnant women required hospitalization, and 2.1% required intensive care.
But according to the DD Isabelle Boucoiran, gynecologist-obstetrician at the CHU Sainte-Justine, pregnant women are also more screened, “because they go to the hospital a lot during pregnancy”. ” [La COVID] is often not the primary cause of their hospitalization. In fact, we see fewer complications than before,” she says.
Conclusion ? Nothing is less clear.
Rising percentage of women with COVID hospitalized may also be just a ‘harvest effect’, Dr.r Vinh. As at-risk or immunocompromised men (with cancer, chronic conditions or other conditions affecting immunity) have been more affected in previous waves, this pool has shrunk, he says. “The virus is more contagious, and there may now be more women likely to be hospitalized who had not previously been infected and who are now. »